The present invention relates to a trap apparatus for trapping reaction byproducts contained in an exhaust gas from a film forming equipment for carrying out a predetermined film forming process on an object, so as to eliminate them.
Generally, in the productions of integrated circuits such as ICs or logic elements, the film forming process for forming a predetermined thin film on an object such as a semiconductor wafer, a glass substrate or LCD substrate, and the etching process for etching a formed thin film into a desired pattern, are repeatedly carried out.
For example, in the film forming process, as a predetermined process gas is introduced into a reaction container, and the process gas reacts, a thin film of silicon, a thin film of a silicon oxide or a silicon nitride, a thin film of a metal, or a thin film of a metal oxide or a metal nitride, or the like is formed on a surface of an object. At the same time with the reaction of forming such a film, undesired reaction byproducts are created, which are discarded together with an exhaust gas.
The reaction byproducts, if directly released to the atmosphere, cause an environmental pollution or the like. Therefore, as a general case, a trap apparatus is provided for the gas exhaust system extending from the processing container, so as to eliminate the reaction byproducts contained in the exhaust gas by trapping them with the trap apparatus.
There are various types of trap apparatuses having different structures, proposed depending upon the characteristics of reaction byproducts to be trapped and eliminated. For example, the trap apparatus used for eliminating reaction products which are liquefied or solidified as a condensate at room temperature, is formed to have a structure consisting of a case having a supply port and an exhaust port, for exhaust gas, and a number of fins provided in the case. It should be noted that these fins are arranged in order each at a different angle with respect to the direction of flow of the exhaust gas, so as to create an exhaust conductance. With this structure, when the exhaust gas passes through the fins, the reaction byproducts contained in the exhaust gas are trapped as they are adhered to the surfaces of the fins.
Trap apparatuses of the conventional type as described above, usually have a single space structure. Due to such a structure, the time period in which the exhaust gas is brought into contact with the fins, is very short. Particularly, when a great amount of process gas is allowed to flow in order to increase the rate of the film formation, reaction byproducts which cannot be trapped by the trap apparatus, in some cases, escape to the down-stream side of the trap apparatus.
Further, in the conventional trap apparatuses, since the fins of a great number, are arranged at the same pitch, the fins are often blinded by the reaction byproducts adhered thereto. Therefore, reaction byproducts which cannot be trapped by the trap apparatus are made to flow to the down-stream of the flow.
As one solution to the above-described problem, it can be proposed to increase the capacity of the trap apparatus. However, if the capacity is simply increased, it is not possible to enhance the trapping efficiency for the increased capacity, but the space occupied by the apparatus is enlarged for nothing.